SIST EN 14620-4:2007

Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -165 °C - Part 4: Insulation components

This European Standard specifies the requirements for materials, design and installation of the insulation of refrigerated liquefied gas (RLG) storage tanks.
RLG storage tanks store liquefied gas with a low boiling point, i.e. below normal ambient temperature.
The concept of storing such products in liquid form and in non-pressurized tanks therefore depends on the combination of latent heat of vaporization and thermal insulation.
Consequently thermal insulation for RLG storage tanks is not an ancillary part of the containment system (as for most ambient atmospheric hydrocarbon tanks) but it is an essential component and the storage tank cannot operate without a properly designed, installed and maintained insulation system.
The main functions of the insulation in RLG storage tanks are:
3   to maintain the boil off below the specific limits;
3   to protect the non low temperature parts/materials of the tank (mainly the outer tank) by maintaining these parts at their required ambient temperature;
3   to limit the cool-down of the foundations/soil underneath the tank to prevent damage by frost heave;
3   to prevent/minimize condensation and icing on the outer surfaces of the tank.
A wide range of insulation materials is available. However the material properties differ greatly amongst the various generically different materials and also within the same generic group of materials.
Therefore within the scope of this European Standard, only general guidance on selection of materials is given.
NOTE   For general guidance on selection of materials see Annex A.
This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C.

Auslegung und Herstellung standortgefertigter, stehender, zylindrischer Flachboden-Stahltanks für die Lagerung von tiefkalt verflüssigten Gasen bei einer Betriebstemperatur zwischen 0 °C und -165 °C - Teil 4: Dämmung

Diese Europäische Norm legt Anforderungen an Werkstoffe, Auslegung und Einbau der Dämmung für Tanks zur Lagerung von tiefkalt verflüssigten Gasen fest.
In RLG Tanks wird verflüssigtes Gas mit niedrigem Siedepunkt gelagert, d. h. mit einem Siedepunkt, der unter der üblichen Umgebungstemperatur liegt.
Das Konzept zur Lagerung von flüssigem Lagergut in nicht unter Druck stehenden Tanks hängt daher von einer geeigneten Kombination der latenten Verdampfungswärme und der Wärmedämmung ab.
Folglich ist die Wärmedämmung für RLG Lagertanks kein untergeordneter Bestandteil des von der/den Sicherheitshülle(n) gebildeten Systems (wie bei den unter Umgebungsbedingungen betriebenen Kohlenwas-serstofftanks), sondern eine sehr wichtige Komponente, weil der Lagertank nur betrieben werden kann, wenn das Dämmsystem vorschriftsmäßig ausgelegt, eingebaut und unterhalten wird.
Die wichtigsten Funktionen der Dämmung in RLG Lagertanks sind:
-   Beibehaltung eines unterhalb der festgelegten Grenzwerte liegenden Siedepunktes;
-   Schutz der nicht für Tieftemperaturen vorgesehenen Tankteile/ werkstoffe (hauptsächlich des Außen-tanks), indem sie bei der jeweils geforderten Umgebungstemperatur gehalten werden;
-   Begrenzung des Abkühlens der Gründungen/des Bodens unter dem Tank, um Beschädigungen durch Frosthub zu verhindern;
-   Verhinderung/Minimierung von Kondensation und Eisbildung an den Außenflächen des Tanks.
Es gibt eine große Bandbreite von Dämmstoffen. Die Eigenschaften der Werkstoffe, die sowohl unterschied-lichen als auch gleichen Werkstoffgruppen zuzuordnen sind, unterscheiden sich jedoch beträchtlich.
Daher wird im Rahmen dieser Norm nur eine allgemeine Anleitung zur Werkstoffauswahl gegeben.
ANMERKUNG   Allgemeine Empfehlungen für die Werkstoffauswahl sind in Anhang A aufgeführt.

Conception et fabrication de réservoirs en acier a fond plat, verticaux, cylindriques, construits sur site, destinés au stockage des gaz réfrigérés, liquéfiés, dont les températures de service sont comprises entre 0 °C et -165 °C - Partie 4: Constituants isolants

La présente Norme Européenne spécifie les exigences pour les matériaux, la conception et l'installation du systeme d'isolation des réservoirs de stockage des gaz liquéfiés réfrigérés (GLR).
Les réservoirs de stockage des GLR assurent le stockage de gaz liquéfiés a bas point d'ébullition, c'est-a-dire en dessous de la température ambiante normale.
Le concept de stockage de tels produits en phase liquide et dans des réservoirs non pressurisés dépend alors de la combinaison entre la chaleur latente d'évaporation et l'isolation thermique.
Par conséquent, l'isolation thermique pour les réservoirs de stockage de GLR ne constitue pas un élément auxiliaire du systeme de confinement (comme c'est le cas pour la plupart des réservoirs de stockage d'hydrocarbures en air ambiant), mais un constituant essentiel, le réservoir de stockage ne pouvant etre mis en oeuvre sans un systeme d'isolation judicieusement conçu, correctement installé et bien entretenu.
Les principales fonctions du systeme d'isolation dans les réservoirs de stockage de GLR consistent a :
-   maintenir le point d'évaporation en dessous des limites spécifiées ;
-   protéger les parties/matieres non soumises a une basse température dans le réservoir (la cuve externe essentiellement) en maintenant lesdits éléments a leur température ambiante requise ;
-   limiter la mise en froid des fondations/du sol sur lequel se dresse le réservoir afin d'éviter les dommages consécutifs au soulevement par le gel ;
-   empecher/réduire au minimum la condensation et la formation de givre sur les surfaces externes du réservoir.
Il existe une large gamme de matériaux isolants. Toutefois, les propriétés des matériaux different considérablement parmi la variété de matériaux génériquement différents, voire également a l'intérieur du meme groupe générique de matériaux.
Par conséquent, dans le cadre du domaine d'application de la présente norme, seules des indications d'ordre général sont données sur le choix des matériaux.

Načrtovanje in proizvodnja na mestu postavitve grajenih navpičnih, valjastih jeklenih posod z ravnim dnom za shranjevanje hlajenih utekočinjenih plinov z delovnimi temperaturami med 0 °C in –165 °C - 4. del: Izolacijski deli

General Information

• Status: Published
• Publication Date: 31-Dec-2006
• ICS: 23.020.10 - Stationary containers and tanks
• Technical Committee: TLP - Pressure vessels
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-2007
• Due Date: 01-Jan-2007
• Completion Date: 01-Jan-2007
• Ref Project: EN 14620-4:2006 - Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -165 °C - Part 4: Insulation components

Relations

• Revised: oSIST prEN 14620-4:2023 - Design and manufacture of site built, vertical, cylindrical, flat-bottomed tank systems for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -196 °C - Part 4: Insulation components
• Effective Date: 01-Apr-2023

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -165 °C - Part 4: Insulation componentsConception et fabrication de réservoirs en acier a fond plat, verticaux, cylindriques, construits sur site, destinés au stockage des gaz réfrigérés, liquéfiés, dont les températures de service sont comprises entre 0 °C et -165 °C - Partie 4: Constituants isolantsAuslegung und Herstellung standortgefertigter, stehender, zylindrischer Flachboden-Stahltanks für die Lagerung von tiefkalt verflüssigten Gasen bei einer Betriebstemperatur zwischen 0 °C und -165 °C - Teil 4: DämmungTa slovenski standard je istoveten z:EN 14620-4:2006SIST EN 14620-4:2007en23.020.10UH]HUYRDUMLStationary containers and tanksICS:SLOVENSKI
STANDARDSIST EN 14620-4:200701-januar-2007







EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14620-4
September 2006 ICS 23.020.10 English Version
Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -165 °C - Part 4: Insulation components
Conception et fabrication de réservoirs en acier à fond plat, verticaux, cylindriques, construits sur site, destinés au stockage des gaz réfrigérés, liquéfiés, dont les températures de service sont comprises entre 0 °C et -165 °C - Partie 4: Constituants isolants
Auslegung und Herstellung standortgefertigter, stehender, zylindrischer Flachboden-Stahltanks für die Lagerung von tiefkalt verflüssigten Gasen bei einer Betriebstemperatur zwischen 0 °C und -165 °C - Teil 4: Dämmung This European Standard was approved by CEN on 20 February 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36
B-1050 Brussels © 2006 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14620-4:2006: E



EN 14620-4:2006 (E) 2 Contents Page Foreword.3 1 Scope.4 2 Normative references.4 3 Terms and definitions.6 4 Design requirements, performance characteristics, testing and selection of insulating materials.6 4.1 General.6 4.2 Analysis of design requirements.6 4.3 Assessment of the performance characteristics.7 4.4 Testing of materials and systems.10 5 Protection of insulation – water vapour barrier.11 5.1 General.11 5.2 Protective structure formed by the outer tank.11 5.3 Protective cover for external insulation.11 6 Design of insulation system.12 6.1 General.12 6.2 Thermal design.12 6.3 Structural design.13 6.4 Insulation for each tank component.15 6.5 Design for different types of containment.19 7 Installation.19 7.1 Introduction.19 7.2 General requirements.19 7.3 Inspection and testing.20 Annex A (informative)
Insulation materials.21 Table A.1 — Single and double containment tanks.21 Table A.2 — Full containment tanks.22 Table A.3 — Membrane tanks.23 Annex B (normative)
Test methods.24 Table B.1 — Testing thermal resistance properties.24 Table B.2 — Testing mechanical properties.25 Table B.3 — Testing temperature resistance.26 Table B.4 — Testing permeability for/effects of water and water vapour properties.26 Table B.5 — Testing of material behaviour in presence of product.27 Table B.6 — Testing chemical properties.27 Table B.7 — Testing fire resistance/reaction to fire.28 Annex C (normative)
Tank bottom insulation - Limit state theory.29 Bibliography.31



EN 14620-4:2006 (E) 3 Foreword This European Standard (EN 14620-4:2006) has been prepared by Technical Committee CEN/TC 265 “Site built metallic tanks for the storage of liquids”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 2007, and conflicting national standards shall be withdrawn at the latest by March 2007. EN 14620 Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and -165 °C consists of the following parts:  Part 1: General;  Part 2: Metallic components;  Part 3: Concrete components;  Part 4: Insulation components;  Part 5: Testing, drying, purging and cool-down. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.



EN 14620-4:2006 (E) 4 1 Scope This European Standard specifies the requirements for materials, design and installation of the insulation of refrigerated liquefied gas (RLG) storage tanks. RLG storage tanks store liquefied gas with a low boiling point, i.e. below normal ambient temperature. The concept of storing such products in liquid form and in non-pressurized tanks therefore depends on the combination of latent heat of vaporization and thermal insulation. Consequently thermal insulation for RLG storage tanks is not an ancillary part of the containment system (as for most ambient atmospheric hydrocarbon tanks) but it is an essential component and the storage tank cannot operate without a properly designed, installed and maintained insulation system. The main functions of the insulation in RLG storage tanks are:  to maintain the boil off below the specific limits;  to protect the non low temperature parts/materials of the tank (mainly the outer tank) by maintaining these parts at their required ambient temperature;  to limit the cool-down of the foundations/soil underneath the tank to prevent damage by frost heave;  to prevent/minimize condensation and icing on the outer surfaces of the tank. A wide range of insulation materials is available. However the material properties differ greatly amongst the various generically different materials and also within the same generic group of materials. Therefore within the scope of this European Standard, only general guidance on selection of materials is given. NOTE For general guidance on selection of materials see Annex A. This European Standard deals with the design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0 °C and –165 °C. 2 Normative references The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 826:1996, Thermal insulating products for building applications — Determination of compression behaviour EN 1604, Thermal insulating products for building applications — Determination of dimensional stability under specified temperature and humidity conditions EN 1606, Thermal insulating products for building applications — Determination of compressive creep EN 1607, Thermal insulating products for building applications — Determination of tensile strength perpendicular to faces EN 1608, Thermal insulating products for building applications — Determination of tensile strength parallel to faces



EN 14620-4:2006 (E) 5 EN 1609, Thermal insulating products for building applications — Determination of short term water absorption by partial immersion EN 12066, Installations and equipment for liquefied natural gas — Testing of insulating linings for liquefied natural gas impounding areas EN 12086, Thermal insulating products for building applications — Determination of water vapour transmission properties EN 12087, Thermal insulating products for building applications — Determination of long term water absorption by immersion EN 12088, Thermal insulating products for building applications — Determination of long term water absorption by diffusion EN 12090:1997, Thermal insulating products for building applications — Determination of shear behaviour EN 12091, Thermal insulating products for building applications — Determination of freeze-thaw resistance EN 12667, Thermal performance of building materials and products — Determination of thermal resistance by means of guarded hot plate and heat flow meter methods — Products of high and medium thermal resistance EN 12939, Thermal performance of building materials and products — Determination of thermal resistance by means of guarded hot plate and heat flow meter methods — Thick products of high and medium thermal resistance EN 13468, Thermal insulating products for building equipment and industrial installations — Determination of trace quantities of water soluble chloride, fluoride, silicate, sodium ions and pH EN 13471, Thermal insulating products for building equipment and industrial installations — Determination of the coefficient of thermal expansion EN 14620-1:2006, Design and manufacture of site built, vertical, cylindrical, flat-bottomed steel tanks for the storage of refrigerated, liquefied gases with operating temperatures between 0°C and –165 °C — Part 1: General EN ISO 62, Plastics — Determination of water absorption (ISO 62:1999) EN ISO 3582, Flexible cellular polymeric materials — Laboratory assessment of horizontal burning characteristics of small specimens subjected to a small flame (ISO 3582:2000) EN ISO 4590, Rigid cellular plastics — Determination of the volume percentage of open cells and closed cells (ISO 4590:2002) EN ISO 4624, Paints and varnishes — Pull-off test for adhesion (ISO 4624:2002) ISO 844, Rigid cellular plastics — Determination of compression properties ISO 4897, Cellular plastics — Determination of the coefficient of linear thermal expansion of rigid materials at sub-ambient temperatures ISO 8301, Thermal insulation — Determination of steady-state thermal resistance and related properties — Heat flow meter apparatus ISO 8302, Thermal insulation — Determination of steady-state thermal resistance and related properties — Guarded hot plate apparatus



EN 14620-4:2006 (E) 6 3 Terms and definitions For the purpose of this European Standard, the terms and definitions given in EN 14620-1:2006 apply. 4 Design requirements, performance characteristics, testing and selection of insulating materials 4.1 General The selection of the appropriate insulation system and materials shall be based on the following:  analysis of design requirements (see 4.2).  assessment of the performance characteristics of the materials (see 4.3). For the insulation materials used, see Annex A. 4.2 Analysis of design requirements 4.2.1 General The thermal insulation system as a whole and each component of it separately, shall be designed taking into account the following design requirements. 4.2.2 Thermal resistance 4.2.2.1 Normal operation of the tank All factors contributing to heat in-leak through the insulation system shall be considered, such as:  product temperature;  external temperature and other climatic conditions (solar radiation, wind, humidity etc.);  thermal conductivity; NOTE A safety margin to be built in for influences of degradation through ageing.  thermal convection;  heat in-leak through radiation;  heat in-leak through cold bridges (from insulation system or tank design). 4.2.2.2 Accidental conditions In addition, accidental conditions shall be considered. These shall include:  required thermal resistance, specified for each component of the insulation and the designed duration of the accidental condition;  thermal resistance offered by the insulation under these conditions.



EN 14620-4:2006 (E) 7 4.2.3 Structural requirements The insulation system shall be designed for the following structural requirements:  static and dynamic actions in all directions;  liquid tightness (if required). 4.2.4 Specific design requirements In addition to the above thermal and structural requirements, the tank insulation design shall fulfil all the specific design requirements that are inherent with the selected specific insulation system, material, installation method and type of containment. These shall be specified on a case-by-case basis. 4.3 Assessment of the performance characteristics 4.3.1 General Based on the design requirements, the required performance characteristics of the insulation materials in the operating temperature range shall be determined. As a minimum the subjects described in 4.3.2 to 4.3.8 shall be considered. 4.3.2 Thermal resistance The following shall be considered:  thermal conductivity: 1) over the required temperature range; 2) in the intended environment, external and internal (product vapour space, purged space, contact with liquid product); 3) taking into account ageing effects over the tank design lifetime;  possible heat in-leak through radiation;  possible heat in-leak through convection (permeability of the insulation material and of the complete insulation system);  heat in-leak through cold bridges. For testing of thermal resistance, see Table B.1. 4.3.3 Mechanical properties The following shall be considered:  compressive properties both at short- and at long-term (creep);  tensile and shear properties for insulation on which lateral forces may act (e.g. earthquake). NOTE Tensile properties may also be required for assessment of thermo-mechanical loads and thermal stresses.  adhesive strength for insulation systems, which are installed by adhesion.



EN 14620-4:2006 (E) 8 For testing of mechanical properties, see Table B.2. 4.3.4 Temperature resistance The insulation shall withstand the temperatures (maximum and minimum service temperatures) and temperature variations to which it may be exposed. Therefore, shrinkage, expansion and possible cracking effects shall be determined, taking into account:  coefficient of thermal expansion, contraction;  tensile strength, tensile modulus in the designed temperature ranges. For testing of temperature resistance, see Table B.3. 4.3.5 Resistance to water and water vapour To assess the possible negative effects of water and water vapour on the insulation, the following characteristics shall be considered:  closed cell content;  permeability for water vapour;  water absorption. In addition, the consequential effects of water and water vapour penetration shall be assessed:  reduction of thermal resistance;  possible structural damage to the insulation by liquid water or by the process of freezing (possibly freeze/thaw cycles). For testing permeability of water and water vapour, see Table B.4. 4.3.6 Influences of stored product The following characteristics shall be assessed:  closed cell content (as indication of open/closed cellular structure);  absorption of product vapours and effect on other material properties (thermal conductivity, mechanical properties, fire resistance);  absorption of/and permeability for liquid product;  effects of long term liquid absorption on other material properties;  desorption behaviour: time/percentage. NOTE
The influence of the stored product on an internal insulation system is critical, as it is often continuously in contact with product vapours and it can come in direct contact with the liquid product in case of an accidental leakage. For testing of material behaviour in presence of product, see Table B.5. 4.3.7 Chemical properties An assessment shall be made of the compatibility between and/or possible chemical reactions of:



EN 14620-4:2006 (E) 9  insulation system, including all its constituents: 1) insulation materials; 2) ancillary products (paints, adhesives, mastics, sealants, coatings etc.); 3) its protective layer (cladding and fastening);  its environment: 1) for external insulation: ambient conditions, water, water vapour, contaminants in air and water; 2) for internal insulation: the product vapours and liquid, inerting/purging gas;  tank material and/or its coating in contact with the insulation system. Typical chemical characteristics to be assessed shall be:  for external insulation: 1) resistance to corrosion of the insulation system itself (or parts of it) in conditions representative for the site location, e.g.: marine atmosphere, atmosphere polluted by chemical industries; 2) corrosion protective or corrosion activating properties of the insulation, e.g.: possibility of dissolving or leaching out corrosive products from the insulation, corrosion protection in case of waterproof insulation system;  for internal insulation: 1) chemical resistance of the insulation system against the product vapours/liquids in the tank; 2) insulation to be inert for the products stored in the tank (absence of contaminants, chemical reagents). For methods of assessing the chemical properties, see Table B.6



EN 14620-4:2006 (E) 10 4.3.8 Reaction to fire The following important aspects shall be considered:  fire risk during construction;  behaviour in case of an external fire (if specified). In view of this, the following characteristics shall be considered:  reaction to fire: 1) flammability; 2) fire retarding properties; 3) toxic gas generation;  maximum temperature limits of the material: melting temperature, decomposition temperature, ignition temperature;  fire resistance properties of the insulation (in case the thermal insulation is designed also for the dual role of fire protection). For methods of assessing fire resistance and reaction to fire, see Table B.7 4.4 Testing of materials and systems 4.4.1 General The performance characteristics of the insulation materials shall be demonstrated by:  laboratory testing,  mock-up testing of an insulation system, NOTE 1 For evaluating the behaviour of a tank insulation system under a combination of various actions, the testing of single material properties may not be sufficient. Mock-up testing is an alternative solution. or  complete installed tank insulation system. NOTE 2 Finite element calculations may provide additional information. 4.4.2 Test methods Whenever available, standardized testing methods shall be in accordance with Annex B. NOTE Annex B deals with testing of performance characteristics of insulation materials/insulation systems. Other tests, used only for specific products, are not covered e.g. measurements of density, dimensions etc. The insulation material manufacturer normally provides them.



EN 14620-4:2006 (E) 11 5 Protection of insulation – water vapour barrier 5.1 General As the insulation system is not a self-standing structural component of the tank, the insulation shall be fixed against, placed upon, poured in between or supported by other structural components (concrete and steel). Furthermore insulation materials shall be protected against various types of possible deterioration and damage, such as:  mechanical damages;  water absorption by rain, snow etc.;  deterioration by other climatic factors such as wind, hail, UV;  water absorption and ice formation by penetration of water vapour;  fire damage. For this protection a protective cover shall be provided. The complete package of insulation material and protective cover and fixing system is called the “Insulation system”. 5.2 Protective structure formed by the outer tank In many containment types, the outer tank provides the protection and the supporting structure for the insulation and, in this case, it shall be confirmed that the outer tank provides sufficient tightness. In cases where the outer tank is made of concrete, which is permeable for water vapour and product vapour, the necessary measures shall be taken to make the concrete water vapour and product vapour tight. Water vapour and product vapour tightness shall be achieved by:  either a metallic liner;  or a Polymeric Vapour Barrier (PVB). NOTE See also EN 14620-3:2006, Clause 9. 5.3 Protective cover for external insulation Where the insulation is placed externally, an appropriate cover shall be provided. This cover shall give protection against all factors that could adversely affect the quality/efficiency and lifetime of the insulation. The following factors shall be considered:  weather factors: 1) water vapour; 2) rain, snow, hail; 3) wind, storm; 4) solar radiation, UV;



EN 14620-4:2006 (E) 12  other atmospheric factors: 1) pollution; 2) corrosion;  mechanical damages by humans, birds etc.;  fire damage. Since for cold insulation, the most detrimental “aggressor”, being invisible and acting continuously, is water vapour, the penetration of water vapour shall be prevented/minimized. For most insulation systems, a good Water Vapour Barrier (WVB) shall be installed on the outside of the insulation to eliminate/minimize water vapour penetration. This WVB shall either be designed separately or as part of the protective cover. The maximum WVB permeability shall be 0,5 g/m² 24 h under the average water vapour pressure differential of the area where the project is located. The protective cover and water vapour barrier of external tank insulation shall be:  metallic (insulation cladding), or  non-metallic (polymeric vapour barrier, vapour barrier mastics), or  a combination of both. NOTE The need for this WVB may be waived for certain insulation systems if it is sufficiently proven that the insulation itself is and remains water vapour tight. 6 Design of insulation system 6.1 General In general, the design of the tank insulation system shall be based on structural and thermal requirements. In addition, the installation method and the commissioning and decommissioning (purging, gas freeing) requirements shall be taken into account. NOTE The insulation design can differ substantially, based on the type of containment selected and on the part of the tank under consideration (bottom, wall, roof). It is difficult to specify for each type of containment each subject to be considered and the approach has been taken that only general requirements are mentioned below. As part of the total tank insulation design, all additional requirements inherent with the specific type of containment, part of the tank under consideration, insulation material selected and other project inherent factors shall be clearly specified in the project specification. 6.2 Thermal design The thermal design shall take account of the requirements specified:  maximum allowed boil off;  minimum design temperature of outer tank components;  prevention of icing/condensation on external surfaces of the tank;  prevention of soil freezing.



EN 14620-4:2006 (E) 13 For boil-off, the purchaser shall specify the maximum allowed boil-off per day and the external climatic conditions that shall be taken into account. The thermal design shall result in an insulation system that, by spreading the total allowed heat in-leak over the various parts of the tank, shall satisfy all the above requirements. If in the thermal design of the tank, in addition to the thermal resistance offered by the insulation system, allowance is also made for the thermal resistance of other parts of the tank such as constructional parts (concrete) or vapour spaces inside the tank, this shall only be done in as far as the thermal resistance of these components in the respective position in the tank and in the relevant temperature range is proven. 6.3 Structural design 6.3.1 General The structural design of the insulation system shall be based on the allowable stress or limit state theory. NOTE The limit state theory is recommended when earthquake conditions have a predominant influence. 6.3.2 Load bearing insulation/compressive action 6.3.2.1 General Certain parts of the tank insulation shall be subjected to compressive loads:  tank bottom insulation for all types of containment;  tank bottom and tank wall for membrane tanks;  TPS for bottom and wall. 6.3.2.2 Allowable stress theory 6.3.2.2.1 For brittle materials (e.g. cellular glass) The minimum overall safety factors, between nominal compressive strength σn and design compressive stress shall be as follows: normal operation:
3,00 hydrostatic test: 2,25 earthquake (OBE): 2,00 earthquake (SSE): 1,50 NOTE The overall safety factor makes allowance for influences of column effect, installation, variation on materials and difference of testing. The nominal compressive strength σn shall be determined as follows:  compressive strength shall be measured in accordance with EN 826:1996, Annex A; the results are expressed as maximum compressive strength σm;  average value of a statistically sufficient number of such tests is called the nominal compressive strength σn of this material; the manufacture
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